The invention is based on an injection pump for internal combustion engines, having a pump piston in a pump piston bushing, to which a suction chamber is connected, in which the connection of the suction chamber to the work chamber of the pump is overtaken by the pump piston upon supply onset, and a diversion of the pump pressure at the end of supply is effected by reopening the connection with the suction chamber.
German Offenlegungsschrift No. 25 37 344 discloses an injection pump in which for diverting the pump pressure at the end of supply, the connection between the work chamber and the suction chamber is first opened up, and then further overflow openings are uncovered by the pump piston. In the diversion of the pump pressure at the end of the injection event, the fuel, which is at high pressure, flows via a recess in the pump piston to a chamber on the outside of the pump piston that is defined by a control edge, and this chamber is relieved to the suction chamber when the bores are overtaken. In the overtaking process, while the openings to the suction chamber are being opened, the fuel flows at high pressure back into the suction chamber, which is usually at relatively low pressure, namely a pre-pump pressure. In this outflow process, the rapid pressure relief has been found to cause excessive wear, which might be ascribed to cavitation. In every case, the rapid decrease in pressure affects all the wearing parts and thus limits the service life of the injection pump.